1. Field of the Invention
The invention relates generally to navigation systems and more specifically to navigation receivers with graphic map displays and hypertext buttons driven from a portable document format (PDF) database.
2. Description of the Prior Art
Ships and aircraft have traditionally been important applications of navigation technology. Given the critical needs of such applications, ships and aircraft have tended to be fitted with the latest in navigation technology. Today that technology includes global position system (GPS) navigation receivers. Such GPS receivers can determine three-dimensional earth position and velocity by processing of microwave radio signals transmitted by dozens of orbiting GPS satellites. The accuracy of such determinations is amazing, special purpose GPS receivers can accurately gauge their own position to within a few inches.
The traditional means of communicating a navigation position has been in terms of latitude and longitude. Paper maps with grids marked in latitude and longitude are conventionally consulted to find one""s position on the map. Recent commercial products marketed by Trimble Navigation (Sunnyvale, Calif.) have the ability to dispense with the use of latitude and longitude terminology, and can communicate the user""s position with text on a screen display that provides, e.g., a Thomas Brothers map page number and the number of inches up and over from a corner of the map page that represents the user""s current position. Support for the United States Geological Survey (USGS) 7.5 minute topographic series of maps is also provided by such GPS receivers.
The most recent batch of GPS receivers universally include modest liquid crystal displays (LCDS) that allow more than just text on lines to be communicated to a user. Such displays allow waypoints or target goals to be represented by the distance and direction to them from the currently computed location. Many models further include an arrow or needle and scale indication in graphic form on the screen that indicates the direction to proceed to the waypoint. Such displays side-step the problems that humans encounter when all that one has to go by are positions expressed only in terms of latitude and longitude. Some GPS receivers have a screen mode in which the relative positions of surrounding waypoints are displayed in plan view.
Tremendous advances in fabrication technology and cost reduction in GPS receivers have recently given rise to a new crop of handheld and portable GPS receivers that indicate a user""s position directly on a map representation. For example, pleasure boaters are offered a cartographic GPS receiver by Magellan that uses an LCD to display a boaters position relative to the coastline and hazards. Such map displays actually contain far less detail than standard United States National Oceanic and Atmospheric Administration (US-NOAA) navigation charts, so such charts are still necessary to navigate coastal waters safely. Many such GPS receiver products use xe2x80x9cC-mapxe2x80x9d cartridges that store regional map data in separately-available plug-in modules. The maps are represented by xe2x80x9cbit-mappedxe2x80x9d data that requires large amounts of storage space for even the simplest of graphics images and that loses resolution as one tries to zoom-in for a closer look of the surrounding neighborhood. Therefore, such cartridges are exchanged in the GPS receiver according to the user""s area of interest. But even so, the detail available in such electronic maps is disappointing.
GPS receivers with color map display are being marketed with chart displays, e.g., the Garmin GPSMAP receiver. A built-in worldwide database provides a zoomed out view to the 64-mile level. Postage-stamp sized Garmin xe2x80x9cG-chartsxe2x80x9d include a navionics database for showing detailed information such as depth contours, navigation aid characteristics and restricted area boundaries for individual locations. The screen views may be smoothly scrolled and panned without triggering complete screen redraws.
Even the best of conventional GPS receivers with chart displays lose map resolution and detail as one tries to zoom in. Such detail has traditionally been very costly in terms of storage memory requirements, and so such detail is missing. As the costs of GPS systems continues to decline, such map-based systems will find their way into the hands of progressively more amateur users. For example, the navigation of cars and trucks on the highways using GPS map displays is becoming popular, and a proliferation of products directed to such drivers is beginning to appear at prices ordinary people can afford.
Computer printers were, at one time, principally of the dot-matrix type. Seven or nine horizontal lines of dots were used to construct representations of characters. Hard copy from such printers was unmistakable because of the coarseness of the characters formed. Higher dot densities were ultimately used, but the cost of multiplying the amount of data and storage needed to represent each character is too great in terms of the memory needed. Dot densities as high as three hundred dots-per-inch (DPI) are so fine that the individual dots in a character are no longer apparent and distinctive character fonts can be constructed. These high dot densities also permit very acceptable graphics images to be constructed, stored, viewed on a display and printed. A typical monitor will reduce such xe2x80x9cbit-mappedxe2x80x9d graphics to resolutions of 1024-by-1024 dots to fit on a standard black and white screen. This results in a million bits being needed to represent the screen graphic, shades of gray and color can multiply this requirement many fold.
Laserprinters conventionally have dot resolutions of three hundred DPI. The communication of a whole printed page""s worth of dots would ordinarily require many megabytes of information to be communicated and several minutes to process. Since much of that printed by laserprinters is text, a shorthand is used that communicates so-called xe2x80x9cASCIIxe2x80x9d eight-bit characters for each character to print, line-by-line. Graphics, however are commonly still bit-mapped.
Adobe Systems (Sunnyvale, Calif.) introduced the POSTSCRIPT page description language that allows Apple MACINTOSH computers to reduce the volumes of data and time needed to communicate printing information to a laserprinter. The graphics, such as a circle, are not communicated in terms of which dots in a raster matrix are white or black, but rather in terms of the center position of the circle, its radius and the line weight. A POSTSCRIPT processor in the printer then converts the circle""s description to dot illuminations, for printing at the maximum resolution that the printer can produce. Such graphics can be manipulated in position, size and line weight, e.g., as is necessary to represent zooming into and out of a map display. The representation of graphics as art objects in this way has proven to be tremendously efficient, and does not suffer from a loss of line resolution as one zooms in for closer detail.
Portable document format (PDF) files, e.g., as defined in the commercial market by Adobe Systems, allow the use of computer files that are independent of the application software and operating system to create it. Therefore, PDF files can be readily converted to and from POSTSCRIPT and Apple Computer QUICK-DRAW file types that embed processing language. Each PDF file contains a PDF document and other supporting data. Each PDF document has one or more pages which may contain text, graphics and images in a device and resolution independent format. A PDF document may also contain purely electronic representations such as hypertext links. Each PDF file further contains the version of the PDF specification used in the file and information about the important structures in the file.
A commercial product called PDF WRITER is available to run on both the Apple MACINTOSH and computers running Microsoft WINDOWS (e.g., GDI) that acts as a printer driver for POSTSCRIPT and GDI application programs. A printer driver ordinarily converts operating system graphics and text commands into commands that will be understood by a particular attached printer. Such drivers embed commands into printer command streams for page printing. The PDF WRITER sends such command streams after embedding to a PDF file instead. The resulting PDF files are platform independent, e.g., they may be freely exchanged between MACINTOSH and WINDOWS computers. PDF files are seven-bit ASCII and may be accessed by PDF viewing applications on any platform, e.g., Adobe ACROBAT EXCHANGE running on the MACINTOSH.
Some conventional applications programs produce POSTSCRIPT page descriptions directly because of certain limitations in QUICKDRAW and GDI imaging models, or because they are running on DOS or UNIX computers that have no system-level printer driver. For these applications, POSTSCRIPT page descriptions can be converted to PDF files by commercial products from Adobe called ACROBAT DISTILLER and ACROBAT READER.
The imaging model of the POSTSCRIPT language is used by PDF to represent text and graphics. A PDF page description draws a page by placing xe2x80x9cpaintxe2x80x9d on selected areas of a blank white page. Painted figures may be letter shapes, regions defined by combinations of lines and curves, or digitally-sampled images of photographs. Such paint can be any color or shade. Any figure can be clipped to another shape, such that only parts of the figure within the shape will appear in the page. PDF uses marking operators similar to POSTSCRIPT marking operators, but it is not a programming language, and so does not include procedures, variables and control constructs. As a result, applications can more efficiently and reliably locate text strings in PDF files, compared to POSTSCRIPT files.
PDF files support industry-standard compression filters like JPEG compression of color and grayscale images, CCITT Group-3 FAX, CCITT Group-4, Lempel-Ziv-Welch (LZW) and run length compression of monochrome images and LZW compression of text and graphics. Such compression is important to maximizing how much page information can be stored by any particular memory and the maximum communication rate needed for any particular connection.
It is therefore an object of the present invention to provide a GPS receiver that stores maps for graphical display in a PDF database.
It is a further object of the present invention to provide a GPS receiver that allows hypertext access of information related to particular points of interest in a PDF map display.
It is a still further object of the present invention to provide a system for the automatic loading of a map database of a mobile GPS receiver with hypertexted-maps of the vicinity.
Briefly, an embodiment of the present invention comprises a GPS navigation receiver connected to a database of maps stored in a portable document format (PDF) file that are independent of any hardware, software and operating system used to create it and that provide for descriptions of documents including any combination of text, graphics and images in a device-independent and resolution-independent format. Hypertext access buttons are provided on an LCD map display for a user to call up data related to points-of-interest represented on a local area map. The GPS receiver indicates the computed position of the user on the map display.
An advantage of the present invention is that a navigation system is provided that offers high map resolution and detail from a database of only a few megabytes.
Another advantage of the present invention is that a mobile navigation system is provided that provides point-of-interest details through hypertext links.
A still further advantage of the present invention is a system and GPS receiver are provided for the automatic loading of a map database of a mobile GPS receiver with maps of the vicinity and hypertext access to local points-of-interest.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the drawing figures.